How to let PHP to create subdomain automatically for each user?

To automatically create a subdomain for each user in PHP, you can use the following steps:

  1. Create a form for users to sign up for an account on your website.

  2. In the form submission handler, use the PHP function substr() to extract the desired subdomain string from the user's chosen username or email address.

  3. Use the PHP function dns_get_record() to check if the subdomain is already in use, and if it is not, create a new DNS record for the subdomain using the PHP function dns_get_record().

  4. Create a new virtual host in your web server's configuration file, pointing to the user's subdomain.

  5. Restart your web server to activate the new virtual host.

  6. Send an email to the user with their subdomain name and a link to their new subdomain.

You will need to have permissions to modify your DNS and web server configurations, as well as have knowledge about DNS and web server. It is also a good practice to validate user input for security reasons, and to have a mechanism for removing subdomains if necessary.